Science Highlights: Ecological Effects of Climate Change

Submitted by admin on 3 November 2014 - 4:24pm

Researchers at NCEAS have produced a groundbreaking body of research exploring the effects of climate change on organisms and their environment. Such impacts are broad and diverse, and include changes to carbon and nutrient cycling, species’ range boundaries, disease risk, life cycles and growth, as well as biodiversity and extinction risks. Over 100 NCEAS projects have brought together multi-disciplinary scientific perspectives, large datasets, and analytical models to examine both the effects of climate change on organisms and the feedback from ecosystems to the climate.

Below is a sampling of some of NCEAS’ most influential and highly cited studies exploring the effects of climate change on organisms and their environment. Many of these studies provide the first global perspective of the ecological effects of climate change, and have informed effective policy making and natural resource management.

Click to expand the accordions below and learn about some of the NCEAS research focused on the ecological effects of climate change.

Effects of Climate Change on Plants and Animals

Many of the defining characteristics of plants and animals, including where they live, seasonal behaviors, potential for coexistence with other species, and relative risk to disease and extinction, are changing in response to climatic conditions. Often these responses are complex, making it difficult to predict large-scale, long-term impacts.

Global biodiversity is changing at an unprecedented rate in response to several human-induced changes in the environment. NCEAS researchers, Sala et al. (2000), identified that behind land use change, climate change is expected to be the second most important driver of biodiversity shifts. They estimate that small changes in temperature or precipitation in arctic, alpine, desert, and boreal forests will result in large changes in species composition and biodiversity.

Research at NCEAS has produced the first comprehensive study of how marine life is responding to climate change. Scientists from 17 institutions synthesized all available marine climate impact studies to produce a database of 1,735 observed changes to marine life. Poloczanska et al. (2013) concluded that marine species are moving poleward to cooler waters at an average of 72 kilometers per decade — considerably faster than terrestrial species, which are moving at an average of 6 kilometers per decade. This is occurring even though sea surface temperatures are warming three times slower than land temperatures. The report forms part of the Fifth Assessment Report of the United Nations Intergovernmental Panel for Climate Change (IPCC).

Many pathogens are sensitive to temperature, rainfall, and humidity; therefore, climate change may impact pathogen development and survival rates, disease transmission, and host susceptibility. A comprehensive study conducted at NCEAS was the first to analyze disease epidemics across entire ecosystems and investigate the impacts of climate change on disease risk. Harvell et al. (2002) concluded that climate change is triggering disease epidemics around the world, as warmer summers and milder winters favor the growth and spread of pathogens. This suggests that disease risk will increase with temperature for a wide range of hosts, including corals, oysters, plants, birds, and humans.

In response to climate change, species are expected to experience shifts in phenology—the seasonal timing of biological activities, such as flowering, breeding, and migrations. NCEAS scientists, Wolkovich et al. (2012), assessed data from four continents and 1,634 plant species and found that warming experiments significantly underestimated how plants will respond to climate change. When compared to long-term observational studies, warming experiments underpredicted phenological responses by at least fourfold.

In response to warming, many terrestrial species are expected to shift their natural ranges—the locations in which they can survive and reproduce. Parmesean et. al. (1999) provided the first large-scale evidence of poleward shifts in entire species’ ranges, concluding that among a sample of 35 non-migratory European butterflies, 63% have ranges that have shifted north during the past century. These NCEAS researchers linked range shifts to climate change by collaborating with European researchers to rule out other factors, such as land use changes, that could have caused the observed geographical trend.

Carbon Dynamics and Ecological Responses

Climate controls ecosystem processes such as the flow of energy through organisms and the physical environment. At the same time, ecological processes participate in the storage and flux of carbon dioxide and other greenhouse gases, thereby affecting future climate. Understanding these dynamics and feedbacks is critical to interpreting and predicting ecological responses to climate change at the global scale.

Arctic and boreal ecosystems play crucial roles in the climate system. They have large effects on the atmosphere through energy exchange and carbon sequestration, and they are responsive to even subtle shifts in climate. Therefore, several major North American research programs have studied the way that arctic and boreal ecosystems interact with climate. Combined, these research programs have covered a wide range of topics, but each program by itself has temporal or spatial limitations. To address this at NCEAS, Chapin et al. (2000) integrated the major findings of these programs to describe climate feedbacks that occur in arctic and boreal ecosystems.

Wildfire directly impacts the carbon cycle and climate through release of greenhouse gases, and also indirectly by altering vegetation distribution and structure. However, many climate models fail to adequately account for fire as an integral part of the global climate system. Bowman et al. (2009) concluded that in fact effects of fire on climate change have been underestimated, and intentional deforestation fires alone contribute up to one-fifth of the human-caused increase in emissions of carbon dioxide. In addition, climate change may increase the frequency of severe fires, with potentially significant greenhouse gas feedbacks to the Earth’s atmosphere.

Many studies demonstrate that forests in the Northern Hemisphere absorb a significant amount of atmospheric carbon dioxide, acting as a reservoir, also known as carbon sequestration. However, the magnitude and distribution of these terrestrial carbon sinks remained uncertain prior to a 2002 NCEAS study by Goodale and colleagues. These researchers used national forest inventories from Canada, the United States, Europe, Russia, and China to estimate the amount of carbon absorbed annually by N. Hemisphere forests. They determined that over 80% of the estimated N. Hemisphere terrestrial carbon sink occurred in only one-third of the forested area, in regions that experience fire suppression, agricultural abandonment, and plantation forestry.

Prior to a 2011 NCEAS study by Bastviken and colleagues, freshwater and wetland ecosystems had been largely ignored in calculating global greenhouse gas budgets. Here, scientists analyzed data from 474 freshwater ecosystems and concluded that freshwaters emit methane at a rate equal to 25% of the estimated terrestrial carbon sink. Therefore, this study suggests that the continental greenhouse gas sink may be sizably overestimated.

Net primary productivity (NPP), the rate at which plants convert atmospheric carbon into biomass through photosynthesis, is one of the most critical components of the terrestrial carbon cycle. NCEAS scientists compiled and analyzed NPP, land cover, precipitation, and temperature data from 5,600 locations globally. Del Grosso et al. (2008) found that previous models that relied on precipitation and temperature as predictors of NPP failed to accurately estimate productivity in ecosystems dominated by grasses and shrubs. Consequently, a new model was developed that provides more accurate estimates of how global NPP will respond to climate change and affect climate in the future.

As atmospheric carbon dioxide increases, changes in the global carbon cycle will impact the cycling of another important nutrient: nitrogen. However, the complexity of interactions between the carbon and nitrogen cycles makes it difficult to predict how each cycle will respond to atmospheric carbon dioxide. Through the synthesis of existing experimental data, Luo et al. (2004) developed a new conceptual framework at NCEAS based on the concept of “progressive nitrogen limitation,” where available nitrogen in soil becomes increasingly limiting as carbon and nitrogen are absorbed by long-lived organic matter. This means that in some cases, the amount of carbon dioxide that can be sequestered by plants may be limited by the amount of nitrogen in the soil. Using this framework in climate change models has the potential to reduce uncertainty about global terrestrial carbon sequestration by providing a better understanding of the role of nitrogen.

Permafrost—subsurface soil that remains below freezing for two consecutive years or more—stores billions of metric tons of organic carbon. As global temperatures rise, permafrost thaws and microbes decompose the ancient carbon, releasing methane and carbon dioxide (CO2) into the atmosphere. While collaborating at NCEAS, Schuur et al. (2008) found that thawing permafrost is potentially one of the most significant sources of CO2 from terrestrial ecosystems to the atmosphere in a warming climate, meaning that as temperatures rise and permafrost thaws, the gases that are released will further accelerate warming and perpetuate climate change.

Management and Policy Making in the Context of Climate Change

To inform conservation and policy-making activities, NCEAS research has provided insights for reserve design and natural resource management in the context of the uncertainties and complexities of climate change.

Biological reserves are intended to protect species, communities, and ecosystems in human-dominated landscapes. However, existing protected areas represent relatively small, geographically biased portions of species and habitats, and climate change can exacerbate these biases. With that in mind, NCEAS researchers developed a model to improve reserve design in the context of climate change. Pyke and Fischer (2005) used the model to identify new protected areas that would complement existing reserves in preserving biodiversity, while representing environmental conditions across a range of climate scenarios.

Natural resource management in the face of climate change requires protecting an ecosystem’s ability to respond and adapt to warming temperatures. This may involve tactics like prioritizing the protection of especially resilient species or reducing anthropogenic impacts that exacerbate the effects of climate change. For example, Baskett et al. (2010) compared various protection strategies for corals to inform more focused and efficient conservation priorities. They found that protecting reefs with diverse coral communities and a moderate abundance of stress-tolerant species is more critical than protecting reefs with lower species diversity and high abundance of stress-tolerant species.